This application is based on application Nos. 11-307621, 11-307622 and 11-307623 filed in Japan, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a throw-away tip for use in a cutting process.
2. Description of Related Art
Throw-away tips are known which are adapted to be attached to a holder or the like to function as a cutting tool. Such a throw-away tip is a disposable tip which is changed, rather than polished for reuse, when its cutting edge is worn out. The throw-away tip has cutting ridges provided on respective corners of a generally planar rectangular or triangular base. When one of the corner cutting ridges is worn out, another of the corner cutting ridges is used. Then, the throw-away tip is changed when all the corner cutting ridges are worn out.
However, it is not easy to check how far the cutting ridges of the throw-away tip have been worn. In view of an operating environment, it is particularly difficult to detect the abrasion degree of a cutting ridge currently used for cutting without interrupting the cutting process.
Conventional methods for detecting the abrasion degree of the cutting ridge are as follows:
(1) The cutting process is interrupted, and the throw-away tip is removed from the holder to be observed the cutting ridge by means of a tool microscope or the like.
(2) The abrasion degree of the cutting ridge is estimated by detecting a phenomenon incidental to the abrasion of the cutting ridge. For example, a reduction in cutting ability, an increase in vibration, occurrence of a noise, or the like is detected by a sensor disposed adjacent a working portion on a machine tool, and the A-estimation of the abrasion degree is based on a detection signal from the sensor.
In the method (1), however, the cutting process is interrupted, and the abrasion degree of the cutting ridge cannot quantitatively be determined, so that the abrasion detection cannot accurately be performed.
The method (2) requires a complicated detector, and is less reliable with a poor sensitivity for the detection of the abrasion degree.
One approach to these problems is described in Japanese Unexamined Utility Model Publication No. 3-120323 (1991). This publication discloses a throw-away tip having a sensor line of a conductive film provided along a cutting ridge on a flank thereof. It is also disclosed that the sensor line has a width conforming to an allowable abrasion width. In accordance with the throw-away tip disclosed in the publication, the sensor line is worn as the cutting ridge is worn, so that expiration of the life of the cutting ridge can be detected when the sensor line is cut off.
Further, Japanese Unexamined Patent Publication No. 9-38846 (1997) proposes an ordinary cutting tool (not a throw-away tip) which has a thin film circuit on a flank thereof, wherein expiration of the life of the cutting tool is automatically detected by sensing a change in electrical resistance which occurs due to abrasion of the thin film circuit as the flank is worn.
The provision of the sensor line of the conductive film along the cutting ridge on the flank for the detection of the change in the line resistance is preferable for the detection of the abrasion of the cutting ridge.
Where this approach is applied to the throw-away tip, however, it is difficult in practice to connect the sensor line provided along the cutting ridge to an external detection circuit and the like.
More specifically, the throw-away tip is a disposable tip as described above, and is very small with a size of less than 1 cm3. During the cutting process, the tip in operation is exposed to a cutting fluid (water or oil) and shavings. However, no technique has been established for connecting the sensor line formed on the small throw-away tip to the external detection circuit and the like without any trouble in such a machining environment.
The present invention is to provide a throw-away tip having an abrasion sensor which serves for practical implementation to solve the aforesaid problems.
It is a principal object of the present invention to provide a throw-away tip having an abrasion sensor which, when attached to a holder or the like, ensures electrical connection between a sensor line provided thereon and an external circuit without any trouble in a cutting process.
It is another object of the invention to provide a throw-away tip which features protection of a connection portion between a sensor line provided thereon and an external circuit.
In accordance with the present invention, there is provided a throw-away tip with an abrasion sensor, which includes: a generally planar base having a rake face defined by one of opposite surfaces thereof, a seat face defined by the other surface thereof opposite from the rake face, and a flank defined by a side face thereof intersecting the rake face and the seat face; and a cutting ridge defined by an intersection between the rake face and the flank, the throw-away tip comprising: a sensor line of a conductive film provided along the cutting ridge on the flank in an electrically insulative relation with respect to the base; a pair of contact regions provided on the seat face in an electrically insulative relation with respect to the base, the contact regions being electrically connectable to a predetermined circuit; and a pair of connection lines provided on the base in an electrically insulative relation with respect to the base and respectively connecting the pair of contact regions to opposite ends of the sensor line, one of the pair of connection lines including a return line spaced a predetermined distance from the sensor line in a parallel relation to the sensor line.
With this arrangement, the provision of the return line extending parallel to the sensor line reduces the area of a region surrounded by an electrical conduction path including the pair of contact regions, the pair of connection lines and the sensor line. Therefore, even if the base has a small surface area, particularly with a small side face or a small flank, the electrical conduction path can properly be provided.
Particularly, where the throw-away tip has a plurality of cutting corner portions and sensor lines provided for the respective corner portions, connection lines for connection to the sensor lines can be arranged in a smaller space.
The connection lines may each have a greater width than the sensor line.
The connection lines which have a greater width than the sensor line have a lower electrical resistance than the sensor line. At detection of a change in the resistance of the sensor line, the resistance of the connection line is relatively low and, therefore, hardly influences the change in the sensor line resistance. As a result, the change in the sensor line resistance can accurately be detected.
It is preferable that the base has a plurality of side faces, which respectively define flanks, and a cutting corner portion is defined by an intersection between the rake face and each adjacent pair of flanks. Preferably, the sensor line extends along the cutting ridge as surrounding the corner portion and the return line extends parallel to the sensor line as surrounding the corner portion.
The return line surrounds the corner portion in a parallel relation to the sensor line which also surrounds the corner portion. Therefore, one end of the sensor line and an end of the return line extending from the other end of the sensor line toward the one end of the sensor line can be located on one of the adjacent pair of flanks. Thus, the pair of connection lines respectively connected to the sensor line and the return line can be provided in a spaced and parallel relation on the same flank. Further, the provision of the connection lines requires a smaller space, so that connection lines for the plurality of sensor lines can be provided on the single flank.
The pair of connection lines except the return line preferably extend parallel to each other at a predetermined inclination angle with respect to the sensor line on the flank.
With the connection lines provided parallel to each other at the predetermined inclination angle with respect to the sensor line, connection lines for the plurality of sensor lines can easily be provided on the flank.
The throw-away tip may include a plurality of cutting corner portions, a plurality of sensor lines for the respective cutting corner portions, plural pairs of connection lines connected to the respective sensor lines, and plural pairs of contact regions, wherein electrical conduction paths including the sensor lines, the pairs of connection lines and the pairs of contact regions are arranged in the same pattern.
By arranging the respective electrical conduction paths including the sensor lines, the pairs of connection lines and the pairs of contact regions in the same pattern, a patterning process can easily be performed, thereby advantageously reducing the production costs.
In accordance with another aspect of the invention, there is provided a throw-away tip with an abrasion sensor, which includes: a generally planar base having a rake face defined by one of opposite surfaces thereof, a seat face defined by the other surface thereof opposite from the rake face, and a flank defined by a side face thereof intersecting the rake face and the seat face; and a cutting ridge defined by an intersection between the rake face and the flank, the throw-away tip comprising: a sensor line of a conductive film provided along the cutting ridge on the flank in an electrically insulative relation with respect to the base; a pair of contact regions provided on the seat face in an electrically insulative relation with respect to the base, the contact regions being electrically connectable to a predetermined circuit; and a pair of connection lines provided on the base in an electrically insulative relation with respect to the base and respectively connecting the pair of contact regions to opposite ends of the sensor line.
The sensor line provided on the throw-away tip is adapted to be connected to probes provided on a tip seat of a holder when the throw-away tip is attached to the holder. The probes extend through the inside of the holder and are connected to an external detection circuit and a judgment circuit.
The tip seat of the holder is adapted to receive the seat face of the throw-away tip brought into abutment or intimate contact therewith. The seat face of the throw-away tip abutting against the tip seat is not exposed to the outside thereby to be directly subjected neither to a cutting fluid (water or oil) nor to slugs. Since the contact regions electrically connectable to the external circuit are provided on the seat face of the throw-away tip, the contact between the contact regions and distal ends of the probes provided on the tip seat can be protected from the cutting fluid and the slugs.
Further, since the probes to be electrically connected to the respective contact regions of the throw-away tip are provided on the tip seat, the probes can be disposed within the holder. Therefore, the electrical connection portions provided on the holder are not exposed from the holder thereby to be affected neither by the cutting fluid nor by the slugs.
Thus, a structure for properly connecting the sensor line of the throw-away tip to the external circuit can be realized. As a result, the expiration of the life of the throw-away tip can accurately be detected with the use of the sensor line.
A side edge of the sensor line away from the cutting ridge preferably extends parallel to the cutting ridge and is spaced from the cutting ridge by a distance predetermined in relation to abrasion of the flank.
With this arrangement, the abrasion of the cutting ridge is related to the cut-off of the conduction of the sensor line, so that a predetermined abrasion state of the cutting ridge can be detected when the conduction of the sensor line is cut off.
The predetermined distance preferably conforms to the life of the cutting ridge which is expired by abrasion of the flank. The expiration of the life of the cutting ridge can be detected when the conduction of the sensor line is cut off.
The base is composed of an insulative material with its surface almost entirely covered with a conductive film, and the sensor line, the connection lines and the contact regions are formed by electrically separating the conductive film on the surface. Alternatively, the base is composed of a conductive material with its surface almost entirely covered with a nonconductive film on which a conductive film is provided, and the sensor line, the connection lines and the contact regions are formed by electrically separating the conductive film on the surface.
The electrical insulation of the sensor line, the contact regions and the connection lines can be achieved by the former method where the base is of the insulative material. Where the base is of the conductive material, the electrical insulation can be achieved by the latter method, in which the surface of the base is covered with the nonconductive film on which the conductive film is formed.
The electrical separation of the sensor line, the connection lines and the contact regions from the conductive film on the surface of the base can be achieved by laser machining. The laser machining ensures a high level of machining accuracy and a high level of flexibility in changing a circuit design.
In accordance with further another aspect of the invention, there is provided a throw-away tip with an abrasion sensor, which includes: a generally planar base having a rake face defined by one of opposite surfaces thereof, a seat face defined by the other surface thereof opposite from the rake face, and a plurality of flanks defined by a plurality of side faces thereof intersecting the rake face and the seat face; a plurality of cutting ridges respectively defined by intersections between the rake face and the flanks; and N cutting corner portions (N: a natural number not smaller than two) each defined by an intersection between the rake face and an adjacent pair of flanks, the throw-away tip comprising: sensor lines of a conductive film respectively provided along the cutting ridges on the N corner portions in an electrically insulative relation with respect to the base to surround the corner portions; N pairs of contact regions provided on the seat face in an electrically insulative relation with respect to the base, the contact regions being electrically connectable to a predetermined circuit; and N pairs of connection lines provided on the base in an electrically insulative relation with respect to the base and respectively connecting the N pairs of contact regions to opposite ends of the sensor lines on the N corner portions.
The throw-away tip has N cutting corner portions on at least one side thereof. The sensor lines for detection of abrasion of the cutting ridges are respectively provided on the N corner portions. The N pairs of contact regions are provided on the seat face for the respective sensor lines. When any one of the corner portions is used for cutting, a pair of contact regions for a sensor line on the currently used corner portion can electrically be connected to probes or the like provided in a holder or the like.
Whichever of the corner portions is used, the abrasion of the cutting ridge on the currently used corner portion can accurately be detected.
The throw-away tip may be a double-sided tip such that, where one of the opposite surfaces of the base serves as the rake face, the other surface serves as the seat face and, where the other surface serves as the rake face, the one surface serves as the seat face. The N corner portions are provided on each of opposite sides of the base, and the N pairs of contact regions are provided on each of the opposite surfaces.
In this case, either side of the throw-away tip can be used, so that the number of the cutting corner portions can be increased. Whichever of the corner portions is used, the abrasion of the corresponding cutting ridge can properly be detected.
It is preferable that one of the contact regions in each of the N pairs is electrically isolated while the other contact regions in the N respective pairs are electrically connected together.
The one contact region in each of the N pairs is a region to which a predetermined voltage is applied from a detection circuit or the like, while the other contact region is a region connected to a ground potential. Therefore, the other contact regions in the N respective pairs serve as common earth regions electrically connected together. Such a configuration of the contact regions is advantageous in that the contact regions can be arranged in a simplified pattern and formed by an easier working process.
The N pairs of contact regions on the one surface of the throw-away tip and the N pairs of contact regions on the other surface are preferably arranged in the same configuration.
It is preferable that the connection lines extend over the flanks and the seat face, and portions of the connection lines on the flanks are inclined at a predetermined inclination angle with respect to the sensor lines.
Since the N pairs of contact regions on the one surface and the N pairs of contact regions on the other surface are arranged in the same configuration, the contact regions on a surface of the base functioning as the seat face can properly be brought into contact with the probes of the detection circuit, whichever surface serves as the rake face.
Where the throw-away tip is adapted for the double-sided use, the N pairs of contact regions are provided on each of the opposite surfaces thereof. The connection lines for connection between the sensor lines and the contact regions should be provided on the respective flanks, since the flanks each have a limited area. Therefore, where the connection lines for connection to the contact regions on the one surface and the connection lines for connection to the contact regions on the other surface are to be provided on the flanks, it is preferable in consideration of the arrangement of the connection lines that the connection lines are inclined with respect to the sensor lines. Thus, the sensor lines and the connection lines can compactly be arranged on the flanks.
The connection lines are preferably arranged symmetrically about the center of each of the flanks. The symmetrical positional relationship of the connection lines about the center of the flank ensures more compact line arrangement.